This application is related to U.S. patent application Ser. No. 623,152 filed on Jun. 21, 1984, and entitled "Apparatus and Method for Providing an Aero-Optical Interface".
This invention relates to structure for providing an optically clear and steady shear layer over a port in the external skin of an airborne vehicle, and a method for achieving such a shear layer.
In certain circumstances it is desired to provide an optically and acoustically stable shear layer over an open port in the external skin of an airborne vehicle so that acoustic resonance in the cavity beneath the port is minimized, and so that light entering or leaving the port is subject to minimal diffusion. One acoustic application is in the wheel well of an aircraft which, in some prior art aircraft, resonates violently upon opening and subjects the structure and hydraulic lines within the cavity to unnecessary vibration. In addition, the noise can actually be heard by passengers and may cause unnecessary nervousness.
Another more recent need for an open port over which the flow is acoustically and optically stable is in infrared scanning of the heavens from an aircraft. The infrared detectors in the scanners are extremely sensitive and the signal processing equipment extremely sophisticated, but unless the optical signal is clear and steady the value of the data is decreased. The clarity (i.e., intensity distribution and size) and steadiness of the optical image are affected by the shear layer over the open port in the airborne vehicle and vary with variations in air density within the shear layer. These density variations have heretofore been studied but little effort has been made to actually control the formation of the shear layer and to influence its properties.